The invention relates to a stacker for flat sheet material such as banknotes, bankpapers, receipts and the like with a cylindrical stacker drum and a transport system, placed tangentially with respect to the stacker drum, and the stacker drum is designed for taking up the sheet material by way of a line of suction openings at its front or leading edge, for pulling the material out of the transport system by turning, moving the material as far as a drum clearer and lastly freeing it for forming a stack, and the leading edge part is pushed flatly by a pushing plate elastically and springingly against the stacker drum.
Such a stacker is part of the prior art, as may be seen, for example, from the German Offenlegungsschrift specification No. 2,555,306. The sheet material, for example banknotes, is run to the stacker drum by way of a belt transporter system tangentially. The leading edge of the banknote is taken up by suction holes, placed in a line on the outer face of the drum, moved round on the drum and out of the transport system and run on to a takeup stack. The stacking is undertaken by moving the leading edge of the banknote as far as a clearing unit stretching up to the outer face of the drum. The clearing unit is used for gripping and stopping the banknote while the drum goes on turning. While stacking is taking place, the stack formed so far is pushed by an elastic pushing plate near the front or leading end of the stack with a low degree of force against the turning stacker drum.
The stacker drum and the transport rollers of the belt transport system are supported on a plate, which may be vertical or horizontal. In the case of a horizontal system, the takeup stack has one long-edge resting on the plate or on a guide of the necessary design.
Dependent on the condition of the banknotes to be stacked, it may be that one or more corners are bent or crumpled forming "dog's ears". If such bent corners are at the leading edge of the banknote in question, that is to say that edge, which is run up against the clearing unit, the stacking of the notes coming after it may be unorderly. The bent corner is in fact something getting in the way of the leading edge, gripped by the suction openings of the stacker drum, of the next banknote, so that the banknote will go into a position at an angle to its desired position, or be turned upwards, before going to the clearing unit. More specially, if the bent corner is at the side, resting on the support plate, of the stack (that is to say the lower edge in the case of a horizontally placed plate), there will be a danger of one or more of the banknotes moved by the stacker drum towards the clearing unit, being hooked by the dog's ear near the lower edge end, because near the top edge they are further transported without anything in their way, at the back they will be turned upwards. Dependent on the size of the bent corner, the trailing end of the banknote will be positioned sticking out of the stack to a greater or lesser degree. On further processing of the stack of banknotes or, for example, on placing label bands round them, such sticking out parts of notes will be the cause of much trouble.